1. Field of the Invention
The present invention relates to a center mechanism of a tire vulcanizer for expanding a bladder to let the bladder closely contacted with the inner circumferential surface of a green tire.
2. Description of the Related Art
In general, in a tire vulcanizer, before vulcanization and patterning of a green tire is performed in a space formed by an upper mold and a lower mold that are clamped, a center mechanism performs shaping, in which a bladder is expanded to be closely contacted with the inner circumferential surface of the green tire, or the like.
Japanese Unexamined Patent Application Publication No. S57(1982)-39942 discloses a center mechanism of a tire vulcanizer, in which the shaping is performed in such a manner that, when a green tire is loaded on a lower mold, a bladder is vertically extended so that the bladder is positioned in a center space of the green tire, and after the green tire is loaded, the bladder is vertically retracted and laterally expanded, so that the bladder is closely contacted with the inner circumferential surface of the green tire.
In this center mechanism of a tire vulcanizer, however, there is a need for lifting an upper mold to above the vertically extended bladder. Thus, it takes a time for the upward and downward movement of the upper mold, a dry cycle time is elongated, and the total height of the tire vulcanizer is increased. In addition, in order to take the bladder away from the green tire after the vulcanization is completed, there is also a need for separately providing a vacuum line for suctioning heat medium in the bladder and retracting the bladder. Thus, the structure of the center mechanism is complicated.
Accordingly, Japanese Unexamined Patent Application Publication No. S51(1976)-17282 discloses a tire vulcanization press device, in which the shaping is performed in such a manner that, when a green tire is loaded on a lower mold, a bladder is placed in a bladder well provided under the lower mold, and after the green tire is loaded, the bladder is inserted into the interior of the green tire and expanded, so that the bladder is closely contacted with the inner circumferential surface of the green tire.
In this tire vulcanization press device, since the bladder is placed in the bladder well, there is no need for a vacuum line for taking the bladder away from the green tire, and the lifting amount of an upper mold can be suppressed. Thus, the total height of a tire vulcanizer is not increased, and hence a dry cycle time can be shortened.
According to the tire vulcanization press device of Japanese Unexamined Patent Application Publication No. S51(1976)-17282, however, the tire is unloaded from the lower mold in such a manner that an upper bead portion of the vulcanized and patterned tire is held between a chuck and a bead ring of the upper mold, and then the upper mold together with the chuck is lifted, while the bladder is taken away from the inner circumferential surface of the tire by lowering each of upper and lower clamps that clamp an upper end portion and a lower end portion of the bladder. That is, the unloading of the tire from the lower mold and the taking of the bladder away from the inner circumferential surface of the tire are performed by separate operations, and working efficiency is not favorable.
In addition, in this tire vulcanization press device, when the bladder is placed, there is a need for vertically arranging cylinders for lifting/lowering the upper and lower clamps below the lower mold so as to lower each of the upper and lower clamps. Further, if these cylinders can not be contained between the lower mold and a base ground, there is a need for digging a pit, in which the cylinders are placed, in the base ground. In this way, when the lowering amounts of the upper and lower clamps are large, the total height of the tire vulcanizer is increased.